AC motors are used in a variety of applications, including vehicle applications such as traction control. The AC motors used in vehicle applications are typically controlled via a voltage source inverter system. Discontinuous Pulse Width Modulation (DPWM) methods are commonly employed in the controllers of voltage source inverter systems to control the fundamental output voltage component of three phase voltage source inverters of the system. These three-phase voltage source inverters may in turn be used to control the phase currents of three phase AC motors. DPWM methods reduce inverter losses in comparison with continuous Pulse Width Modulation (PWM) methods, such as sinusoidal or space vector modulation.
DPWM methods generally differ from continuous PWM methods in that DPWM methods use a single zero vector in a given switching cycle of the three phase voltage source inverter. Additionally, in most DPWM methods, each switch in the three phase voltage source inverter is not switched, or clamped, for sixty degree (60°) segments of an electrical cycle. The location of the sixty degree (60°) clamped segment with respect to the output voltage of the three phase voltage source inverter and the load power factor generally determines the type of DPWM method and resulting PWM properties.
AC motor drives use a measured current at a given sampling instant as a control variable. However, most PWM techniques add a ripple current onto the motor currents that can cause errors in the sampling instant of the motor drive and result in a malfunction or inefficient operation of the AC motor.
Accordingly, it is desirable to provide a method and apparatus for controlling a voltage source inverter system that minimizes current sampling errors in AC motor drives. Additionally, it is desirable to provide a voltage source inventor system for controlling an AC motor that minimizes current sampling errors. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.